This project will study the application of audible sound transmission to the determination of lung structure and early detection of disease. Theory predicts that sound propagation in airways is critically dependent on wall elasticity. This elasticity is dependent on factors including bronchomotor tone and parenchymal support as well as the condition of the intramural connective tissue. Sound will be produced within the airways and the propagation coefficients determined along the airways and the propagation coefficients determined along the airways, through the peripheral lung, and through the thoracic wall. Estimates of lung condition, including elasticity wall be made in vivo from these coefficients. Pulmonary edema, asthma, pulmonary fibrosis, and emphysema are expected to differentially affect sound transmission. These diseases will be produced in dogs. Changes in transmission will be related quantitatively to the functional and histopathologic indicators of disease. This study will record adventitious sounds, particularly rales, from within the lung. The changes due to transmission to points to external auscultation will be characterized. This should provide a basis for better understanding and clinical interpretation of the processes of adventitous sound production.